The use of single-wall carbon nanotubes (SWNTs) in manufacturing and biomedical applications is increasing at a rapid rate; however data on the effects of a potential environmental release of the materials remain sparse. In this study, soils with either low or high organic matter contents as well as pure cultures of E. coli are challenged with either raw As-Produced SWNTs (AP-SWNTs) or SWNTs functionalized with either polyethyleneglycol (PEG-SWNTs) or m-polyaminobenzene sulfonic acid (PABS-SWNTs). To mimic chronic exposure, the soil systems were challenged weekly for six weeks; microbial activities and community structures for both the prokaryote and eukaryote community were evaluated. Results show that repeated applications of AP-SWNTs can affect microbial community structures and induce minor changes in soil metabolic activity in the low organic matter systems. Toxicity of the three types of SWNTs was also assessed in liquid cultures using a bioluminescent E. coli-O157:H7 strain. Although decreases in light were detected in all treated samples, low light recovery following glucose addition in AP-SWNTs treatment and light absorption property of SWNTs particles suggest that AP-SWNTs suppressed metabolic activity of the E. coli, while the two functionalized SWNTs are less toxic. The metals released from the raw forms of SWNTs would not play a role in the effects seen in soil or the pure culture. We suggest that sorption to soil organic matter plays a controlling role in the soil microbiological responses to these nanomaterials.
"Compared with pure cultures and wastewater systems, the soil environment is much more complex and uncontrolled. When graphene enters the soil, it may interact with organic matter or clay minerals present in the soil , stabilizing graphene and making it less bioavailable, which would mitigate the effect of graphene on microbial communities. On the contrary, dissolved organic matter (DOM) might promote the mobility and bioavailability of graphene by acting as natural surfactants . "
"Great attention has been paid to the CNTs' ecological effects on microbe since those microorganisms play key roles in the global biogeochemical cycling of nutrients, biomass decomposition, and waste treatment systems (Kang et al. 2007; Brar et al. 2010). Previous researches have confirmed the adverse impacts of CNTs on both the pure culture bacteria (Kang et al. 2007; Pasquini et al. 2013) and the microbial communities in soil and activated sludge (Goyal et al. 2010; Tong et al. 2012). The antibacterial activity of CNTs enables them to be used in regenerative purification devices to remove viral and bacterial pathogen during waste disposal and purification process (Brady-Estévez et al. 2008). "
[Show abstract][Hide abstract] ABSTRACT: To enrich the understanding on interactions between carbon nanotubes (CNTs) and microbes, the responses of a biphenyl-degrading bacterium to single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs) and carboxyl single-walled carbon nanotubes (SWCNT-COOHs) were investigated. Electron microscopy, viability test, cellular membrane integrity, and oxidative stress analyses indicated that CNT toxicity was mainly caused by physical piercing. Apart from antibacterial activities, the experimental results showed that CNTs enhanced cell growth and biphenyl degradation at certain concentrations (1.0-1.5 mg/L). The CNTs aggregated and adsorbed cells and biphenyl to form a CNTs-cells-biphenyl coexisting system, thus it created a suitable microenvironment for cell attachment and proliferation where the cells could utilize biphenyl easier for their growth. To the best of our knowledge, this is the first report about CNTs' impact on biodegradation efficacy and growth of aromatic-degrading bacterium.
Environmental Science and Pollution Research 10/2015; DOI:10.1007/s11356-015-5532-1 · 2.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Production and use of carbon nanotubes (CNTs) will unavoidably lead to their disposal in the environment. To assess the risk associated with their release, an understanding of their mobility and ultimate fate is essential. To date, however, relatively little research has been conducted on the fate of CNTs in the environment. In this study, phase distributions of multi-walled carbon nanotubes (MWCNTs) between water and soils were determined by classical laboratory batch experiments and compared with values estimated from several prediction models. Aggregation and subsequent sedimentation appeared to be an important process governing the phase distribution of MWCNTs between water and soils. In this respect, corrected LogK oc was calculated by excluding the mass of settled MWCNTs and the values were from 3.73 to 4.64. Octanol-water partition coefficient (K ow) of MWCNTs was also determined to predict the soil sorption property. The LogK oc values estimated from prediction models were from 1.12 to 2.31. These results indicate that the K ow alone may not be an appropriate predictor of K oc for MWCNTs and other predictors or approaches should be explored to accurately estimate the potential mobility of MWCNTs in the environment.
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